Experimental and clinical observations have supported the concept that neuropeptides play central roles in neurotransmission as well as the regulation of secretory functions of adenohypophysial, pancreatic, adrenalcortical and gut cells. Among the thirty or so neuropeptides that have been implicated in neuronal function in the mammalian central nervous system, several have also been suggested to function as neurotransmitters or neuromodulators primarily in afferant neurons. We have suggested that the application of recombinant DNA technology to the analysis of mRNAs of the brain or other neural tissues may provide a means for identifying new transmitter substances and their related proteins. Thus, following the inferential discovery of novel brain and other neuropeptide transmitters via DNA sequencing technologies, it is possible to synthesize the predicted structure of the new peptide, generate antibody to this peptide and establish the existence, by classical immunohistochemical procedure, of this peptide in various neural tissues. Furthermore, the synthetic peptide itself can be used as a source for identifying and investigating its physiological actions.
Calcitonin is a 32-residue, amidated peptide hormone which was earlier isolated and characterized. Calcitonin is found in both the thyroid and the hypothalamus and has the formula: ##STR2## Calcitonin has biological activity in lowering body calcium levels and in promoting absorption of calcium into bone.